dune cache trim: also print number of files removed

Signed-off-by: Nicolás Ojeda Bär <n.oje.bar@gmail.com>

bin/cache.ml

@@ -58,9 +58,14 @@ let trim =
        Dune_cache.Trimmer.trim ~goal
      with
      | Error s -> User_error.raise [ Pp.text s ]
-     | Ok { trimmed_bytes } ->
+     | Ok { trimmed_bytes; number_of_files_removed } ->
        User_message.print
-         (User_message.make [ Pp.textf "Freed %s" (Bytes_unit.pp trimmed_bytes) ])
+         (User_message.make
+            [ Pp.textf
+                "Freed %s (%d files removed)"
+                (Bytes_unit.pp trimmed_bytes)
+                number_of_files_removed
+            ])
 ;;
 
 let size =

src/dune_cache/trimmer.ml

@@ -2,16 +2,21 @@ open Stdune
 open Dune_cache_storage
 
 module Trimming_result = struct
-  type t = { trimmed_bytes : int64 }
+  type t =
+    { trimmed_bytes : int64
+    ; number_of_files_removed : int
+    }
 
-  let empty = { trimmed_bytes = 0L }
+  let empty = { trimmed_bytes = 0L; number_of_files_removed = 0 }
 
   (* CR-someday amokhov: Right now Dune doesn't support large (>1Gb) files on
      32-bit platforms due to the pervasive use of [int] for representing
      individual file sizes. It's not fundamentally difficult to switch to
      [int64], so we should do it if it becomes a real issue. *)
   let add t ~(bytes : int) =
-    { trimmed_bytes = Int64.add t.trimmed_bytes (Int64.of_int bytes) }
+    { trimmed_bytes = Int64.add t.trimmed_bytes (Int64.of_int bytes)
+    ; number_of_files_removed = t.number_of_files_removed + 1
+    }
   ;;
 end
 

src/dune_cache/trimmer.mli

@@ -4,7 +4,10 @@
    from Jenga's trimmer. *)
 
 module Trimming_result : sig
-  type t = { trimmed_bytes : int64 }
+  type t =
+    { trimmed_bytes : int64
+    ; number_of_files_removed : int
+    }
 end
 
 (** Trim the cache by removing a set of unused files so that the total freed